Potential use of metabolic breath tests to assess liver disease and prognosis: has the time arrived for routine use in the clinic?

Serum Levels of Adropin Improve the Predictability of MELD and Child-Pugh Score in Cirrhosis: Results of Proof-of-Concept Clinical Trial

Adropin is a peptide that was suggested to have a role in cirrhosis. The present study aimed to determine the ability to use serum adropin levels to improve their prediction accuracy as an adjunct to the current scores. In a single-center, proof-of-concept study, serum adropin levels were determined in thirty-three cirrhotic patients. The data were analyzed in correlation with Child-Pugh and MELD-Na scores, laboratory parameters, and mortality. Adropin levels were higher among cirrhotic patients that died within 180 days (1,325.7 ng/dL vs. 870.3 ng/dL, p = 0.024) and inversely correlated to the time until death (r ² = 0.74). The correlation of adropin serum levels with mortality was better than MELD or Child-Pough scores (r ² = 0.32 and 0.38, respectively). Higher adropin levels correlated with creatinine (r ² = 0.79. p < 0.01). Patients with diabetes mellitus and cardiovascular diseases had elevated adropin levels. Integrating adropin levels with the Child-Pugh and MELD scores improved their correlation with the time of death (correlation coefficient: 0.91 vs. 0.38 and 0.67 vs. 0.32). The data of this feasibility study suggest that combining serum adropin with the Child-Pugh score and MELD-Na score improves the prediction of mortality in cirrhosis and can serve as a measure for assessing kidney dysfunction in these patients.

Liver fat accumulation more than fibrosis causes early liver dynamic dysfunction in patients with non-alcoholic fatty liver disease

INTRODUCTION

In Non-Alcoholic Fatty Liver Disease (NAFLD), events driving early hepatic dysfunction with respect to specific metabolic pathways are still poorly known.

METHODS

We enrolled 84 subjects with obesity and/or type 2 diabetes (T2D). FibroScan® served to assess NAFLD by controlled attenuation parameter (CAP), and fibrosis by liver stiffness (LS). Patients with LS above 7 kPa were excluded. APRI and FIB-4 were used as additional serum biomarkers of fibrosis. The stable-isotope dynamic breath test was used to assess the hepatic efficiency of portal extraction (as DOB15) and microsomal metabolization (as cPDR30) of orally-administered (13C)-methacetin.

RESULTS

NAFLD occurred in 45%, 65.9%, and 91.3% of normal weight, overweight, and obese subjects, respectively. Biomarkers of liver fibrosis were comparable across subgroups, and LS was higher in obese, than in normal weight subjects. DOB15 was 23.2 ± 1.5‰ in normal weight subjects, tended to decrease in overweight (19.9 ± 1.0‰) and decreased significantly in obese subjects (16.9 ± 1.3, P = 0.008 vs. normal weight). Subjects with NAFLD had lower DOB15 (18.7 ± 0.9 vs. 22.1 ± 1.2, P = 0.03) but higher LS (4.7 ± 0.1 vs. 4.0 ± 0.2 kPa, P = 0.0003) than subjects without NAFLD, irrespective of fibrosis. DOB15 (but not cPDR30) decreased with increasing degree of NAFLD (R = -0.26; P = 0.01) and LS (R = -0.23, P = 0.03). Patients with T2D showed increased rate of NAFLD than those without T2D but similar LS, DOB15 and cPDR30.

CONCLUSIONS

Overweight, obesity and liver fat accumulation manifest with deranged portal extraction efficiency of methacetin into the steatotic hepatocyte. This functional alteration occurs early, and irrespective of significant fibrosis and presence of T2D.

Hepatic fibrosis 2022: Unmet needs and a blueprint for the future

Steady progress over four decades toward understanding the pathogenesis and clinical consequences of hepatic fibrosis has led to the expectation of effective antifibrotic drugs, yet none has been approved. Thus, an assessment of the field is timely, to clarify priorities and accelerate progress. Here, we highlight the successes to date but, more importantly, identify gaps and unmet needs, both experimentally and clinically. These include the need to better define cell-cell interactions and etiology-specific elements of fibrogenesis and their link to disease-specific drivers of portal hypertension. Success in treating viral hepatitis has revealed the remarkable capacity of the liver to degrade scar in reversing fibrosis, yet we know little of the mechanisms underlying this response. Thus, there is an exigent need to clarify the cellular and molecular mechanisms of fibrosis regression in order for therapeutics to mimic the liver's endogenous capacity. Better refined and more predictive in vitro and animal models will hasten drug development. From a clinical perspective, current diagnostics are improving but not always biologically plausible or sufficiently accurate to supplant biopsy. More urgently, digital pathology methods that leverage machine learning and artificial intelligence must be validated in order to capture more prognostic information from liver biopsies and better quantify the response to therapies. For more refined treatment of NASH, orthogonal approaches that integrate genetic, clinical, and pathological data sets may yield treatments for specific subphenotypes of the disease. Collectively, these and other advances will strengthen and streamline clinical trials and better link histologic responses to clinical outcomes.

A History of the Assessment of Liver Performance

Content available: Author Interview and Audio Recording.

LOXL2-A New Target in Antifibrogenic Therapy?

The concept of liver fibrosis and cirrhosis being static and therefore irreversible is outdated. Indeed, both human and animal studies have shown that fibrogenesis is a dynamic and potentially reversible process that can be modulated either by stopping its progression and/or by promoting its resolution. Therefore, the study of the molecular mechanisms involved in the pathogenesis of liver fibrosis is critical for the development of future antifibrotic therapies. The fibrogenesis process, common to all forms of liver injury, is characterized by the increased deposition of extracellular matrix components (EMCs), including collagen, proteoglycans, and glycoproteins (laminin and fibronectin 2). These changes in the composition of the extracellular matrix components alter their interaction with cell adhesion molecules, influencing the modulation of cell functions (growth, migration, and gene expression). Hepatic stellate cells and Kupffer cells (liver macrophages) are the key fibrogenic effectors. The antifibrogenic mechanism starts with the activation of Ly6C^high macrophages, which can differentiate into macrophages with antifibrogenic action. The research of biochemical changes affecting fibrosis irreversibility has identified lysyl oxidase-like 2 (LOXL2), an enzyme that promotes the network of collagen fibers of the extracellular matrix. LOXL2 inhibition can decrease cell numbers, proliferation, colony formations, and cell growth, and it can induce cell cycle arrest and increase apoptosis. The development of a new humanized IgG4 monoclonal antibody against LOXL2 could open the window of a new antifibrogenic treatment. The current therapeutic target in patients with liver cirrhosis should focus (after the eradication of the causal agent) on the development of new antifibrogenic drugs. The development of these drugs must meet three premises: Patient safety, in non-cirrhotic phases, down-staging or at least stabilization and slowing the progression to cirrhosis must be achieved; whereas in the cirrhotic stage, the objective should be to reduce fibrosis and portal pressure.

Prospective Assessment of Liver Function by an Enzymatic Liver Function Test to Estimate Short-Term Survival in Patients with Liver Cirrhosis

BACKGROUND

MELD attempts to objectively predict the risk of mortality of patients with liver cirrhosis and is commonly used to prioritize organ allocation. Despite the usefulness of the MELD, updated metrics could further improve the accuracy of estimates of survival.

AIMS

To assess and compare the prognostic ability of an enzymatic ¹³C-based liver function test (LiMAx) and distinct markers of liver function to predict 3-month mortality of patients with chronic liver failure.

METHODS

We prospectively investigated liver function of 268 chronic liver failure patients without hepatocellular carcinoma. Primary study endpoint was liver-related death within 3 months of follow-up. Prognostic values were calculated using Cox proportional hazards and logistic regression analysis.

RESULTS

The Cox proportional hazard model indicated that LiMAx (p < 0.001) and serum creatinine values (p < 0.001) were the significant parameters independently associated with the risk of liver failure-related death. Logistic regression analysis revealed LiMAx and serum creatinine to be independent predictors of mortality. Areas under the receiver-operating characteristic curves for MELD (0.86 [0.80-0.92]) and for a combined score of LiMAx and serum creatinine (0.83 [0.76-0.90]) were comparable.

CONCLUSIONS

Apart from serum creatinine levels, enzymatic liver function measured by LiMAx was found to be an independent predictor of short-term mortality risk in patients with liver cirrhosis. A risk score combining both determinants allows reliable prediction of short-term prognosis considering actual organ function. Trial Registration Number (German Clinical Trials Register) # DRKS00000614.

Breath test using 13C methacetin does not seem to be useful in the assessment of liver function in girls with anorexia nervosa: a case control study

BACKGROUND

Anorexia nervosa (AN) concerns approximately up to 1.8% of the pediatric female population. One of the complications that can occur in the course of this disease is acute liver failure. This study's objective was to assess the usefulness of the 13C labeled Methacetin Breath Test (MBT) in the diagnostics of the liver function in girls with eating disorders.

METHODS

For the study 81 girls aged 12 to 17 years were recruited, including 41 patients with confirmed diagnosis of AN (mean age 14.7 ± 1.48 years) and 40 age-matched controls. The diagnosis was based on the present Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria. Weight and height were measured in all study participants and the Body Mass Index (BMI) was calculated. In the study and control group laboratory tests assessing the liver function and the MBT were performed.

RESULTS

In all controls the anthropometric as well as laboratory liver function parameters were normal. In the study group 25 patients (61%) had BMI below the lower limit for age. The total percentage of 13CO2 recovery in the 120th minute of the test did not exceed the lower limit in patients and controls. A result of the 13CO2 cumulative recovery above the upper normal range was found in 18 girls with AN (44% of the study group) and 2 controls (5%). Patients with AN were characterized by significantly higher 13CO2 cumulative dose recovery after ingestion of the substrate in comparison to the control group in all time points of the test.

CONCLUSIONS

The obtained results confirm a significant stimulation of the liver metabolism of 13C labeled methacetin in female patients with AN. The increased cumulative dose recovery of the substrate in girls with AN impacts the credibility of this measurement and implies a risk of false negative results.

Autofluorescence-based optical biopsy: An effective diagnostic tool in hepatology

Autofluorescence emission of liver tissue depends on the presence of endogenous biomolecules able to fluoresce under suitable light excitation. Overall autofluorescence emission contains much information of diagnostic value because it is the sum of individual autofluorescence contributions from fluorophores involved in metabolism, for example, NAD(P)H, flavins, lipofuscins, retinoids, porphyrins, bilirubin and lipids, or in structural architecture, for example, fibrous proteins, in close relationship with normal, altered or diseased conditions of the liver. Since the 1950s, hepatocytes and liver have been historical models to study NAD(P)H and flavins as in situ, real-time autofluorescence biomarkers of energy metabolism and redox state. Later investigations designed to monitor organ responses to ischaemia/reperfusion were able to predict the risk of dysfunction in surgery and transplantation or support the development of procedures to ameliorate the liver outcome. Subsequently, fluorescent fatty acids, lipofuscin-like lipopigments and collagen were characterized as optical biomarkers of liver steatosis, oxidative stress damage, fibrosis and disease progression. Currently, serum AF is being investigated to improve non-invasive optical diagnosis of liver disease. Validation of endogenous fluorophores and in situ discrimination of cancerous from non-cancerous tissue belong to the few studies on liver in human subjects. These reports along with other optical techniques and the huge work performed on animal models suggest many optically based applications in hepatology. Optical diagnosis is currently offering beneficial outcomes in clinical fields ranging from the respiratory and gastrointestinal tracts, to dermatology and ophthalmology. Accordingly, this review aims to promote an effective bench to bedside transfer in hepatology.

13C Methacetin Breath Test for Assessment of Microsomal Liver Function: Methodology and Clinical Application

Assessment of the liver function, and the need of constant monitoring of the organ's capacity, concerns not only patients with primary liver diseases, but also those at risk of hepatopathies secondary to other chronic diseases. Most commonly, the diagnostics is based on measurements of static biochemical parameters, which allow us to draw conclusions only indirectly about the function and the degree of damage of the organ. On the other hand, liver biopsy is an invasive procedure and therefore it is associated with a considerable risk of complications. Dynamic tests enable us to assess quantitatively the organ's functional reserve by analyzing the kinetics of the metabolization of the substrate by the liver. In practice applied are breath tests using substances such as aminopyrine, caffeine, methacetin, erythromycin (for assessment of the microsomal function); phenylalanine, galactose (for assessment of the cytosolic function); methionine, octanoate, ketoisocaproic acid (for assessment of the mitochondrial function). The test with ¹³C methacetin belongs to the best described and most widely applied methods in noninvasive liver function assessment. Due to the rising availability of this method, knowledge concerning its limitations and controversies regarding the methodology, as well as its usefulness in chosen groups of patients, seems to be vital.